ppp has asked for the wisdom of the Perl Monks concerning the following question:

I am perl beginner and under a situation where i have a dongle (USB internet key). When USB is connected and i do : 

$address='Net::Address::IP::Local'->public ;

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then it works fine and return an IP address. But i have situation where i have to check disconnect the USB and then check it's IP address using same code but on disconnection it gives an error on writing this command and it is: 

Unable to create UDP socket: A socket operation was attempted to an un
+reachable
network. at C:/Perl/site/lib/Net/Address/IP/Local.pm line 166.

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Yes ofcourse it will give error because it will not return any IP address when disconnected. But i wann handle this error. And assign a static IP when it is disconnected like "192.80.13.1". I tried to handle this error this way but out of success: 

sub ReturnIpAddress 
{
  if( 'Net::Address::IP::Local'->public =~ m/^(\d\d?\d?)\.(\d\d?\d?)\.
+(\d\d?\d?)\.(\d\d?\d?)$/ )
  {
    return $address= 'Net::Address::IP::Local'->public; #When i try to
+ print this address it print nothing s it crashes because of the erro
+r due to the enteres command i discussed before.
  }
  else
  {
    return $address='192.80.160.16';
  }        
}

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How to handle this error and assign statically $address='192.80.160.16' when USB key is disconnected ?

Replies are listed 'Best First'.
Re: Why 'Net::Address::IP::Local'->public do not return IP address
by Laurent_R (Canon) on Jan 16, 2015 at 18:31 UTC
    Try to put your block of code in an eval function (and make sure to check the content of the $@ special variable).
    Je suis Charlie.
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      you mean something like this : eval { $address='Net::Address::IP::Local'->public =~ m/^(\d\d?\d?)\.(\d\d?\d?)\.(\d\d?\d?)\.(\d\d?\d?)$/ }; warn $@ if $@;
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        Well, yes, something like that, or possibly including a bit more of your code in the eval block. You should also probably check the value returned by eval, it might be useful.

        I can't test right now anything really similar to your code, but this "several-liner" should give you an idea of how the eval function works: 

        perl -E '
use strict;
use warnings;

my $output;

say "successful statement";
$output = eval {my $c = 4 + 5;};
printout ($output, $@);

say "division by 0";
$output = eval {my $c = 4/0;};
printout ($output, $@);

say "statement with die";
$output = eval {die "I am dieing\n";};
printout ($output, $@);

sub printout {
    my ($out, $diag) = @_;
    say $out, "\t", $diag, "\n" if defined $out;
    say "\t\t$diag" unless defined $out;
}
'
successful statement
9

division by 0
                Illegal division by zero at -e line 12.

statement with die
                I am dieing

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        Je suis Charlie.
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